REPORT ON ATMOSPHERIC ELECTRIC WORK 



41 



the diurnal-variation observations but some of its fea- 

 tures could be introduced into the regular daily schedule 

 without appreciably increasing the intensity of the work. 



The schedule provides for the recording conductivity 

 apparatus when that is installed. It is hoped it will be 



possible to try this schedule and that the Carnegie staff 

 and observers who have had experience in this work will 

 study it with a view to arriving at a schedule for the rest 

 of the cruise after San Francisco. 



APIA, SAMOA TO YOKOHAMA, JAPAN, APRIL 20 TO JUNE 6, 1929 



General. - -Daily observations of the atmospheric- 

 electric elements have been made as before. For the 

 first week after leaving Apia it was necessary to use the 

 main engine at times in order to reach the trade wind 

 belt and conditions therefore were not favorable for a 

 complete program. Between April 27 and May 28 good 

 weather conditions prevailed. Diurnal-variation 24- 

 hour runs were made on April 30 and May 1 , May 9 and 

 10, 17 and 18, and 27 and 28. 



Potential-Gradient Recorder. --Between April 28 and 

 May 28 complete records were obtained, excluding the 

 five days during which the vessel was moored in Guam 

 harbor. Calibrations and leak tests have been made as 

 before. Soon after leaving Guam it was noticed that the 

 deflections were much smaller than those previously 

 obtained and it was suspected that the sensitivity had 

 changed appreciably. A calibration made on May 28 

 showed that this was the case. It was found that the ma- 

 rine plug in the auxiliary potential line (the Eveready 

 "B" battery supplying the inner-case potential is locat- 

 ed in the control room) had become badly corroded. 

 The plug was thoroughly cleaned and another calibration 

 made on May 30. It is important, of course, to be able 

 to tell just when a change of sensitivity such as this oc- 

 curs, and, to some extent, the potential applied daily 

 for leak tests affords a rough check. In this case the 

 change evidently occurred sometime during the period 

 when the recorder was out of operation in Guam. In the 

 iuture the recorder will be operated while In port even 

 though the presence of surrounding objects makes the 

 results of little value. Negative potentials have occurred 

 on eight occasions but at no time has the potential re- 

 mained negative for more than a few minutes. 



Between April 10 and 13, whUe at Apia, the record- 

 er was operating on the ship under varying mainsail, 

 boom, and awning conditions and the hourly scalings 

 from these records have been made and checked. As 

 soon as the figures are available the scalings will be 

 compared with the hourly values obtained from the Benn- 

 dorf recorder in the reef house (designated Lagoon 

 House) of the Apia Observatory. Alter an inspection of 

 the standardizing station used by Mr. Thomson of the 

 Apia Observatory staff, it was questioned whether the 

 reduction factor (1.00) adopted by the Observatory for 

 the Lagoon House was valid. To test this, eye observa- 

 tions were made, during the hours of low tide, on Wat- 

 son's Island--an ideal location for this work, as it was 

 about midway between the Lagoon House and the Carne- 

 gie . One disadvantage of the Observatory's standardi- 

 zing site Is that it Is closely hemmed in by mangrove 

 swamp and cocoanut trees; another, is that It is not pos- 

 sible to observe there for more than one hour at a time. 

 The eye observations on April 11 were quite successful, 

 five consecutive hours being obtained. The resulting 

 ratioB are: 



Island 

 Lagoon 



0.731 



Island 

 Land 



1.086 



Land 

 Lagoon 



= 0.682 



(Island observations were made by eye-reading apparatus 

 and Land bythe recorder at the observatory land station.) 

 The work on the following day, April 12, was seriously 

 interfered with by a severe thunderstorm which swept 

 the island of Upolu from east to west and the observa- 

 tions may be considered worthless. It appears quite defi- 

 nite from the alwve ratios that the reduction factor for 

 both land and lagoon stations cannot be 1.00 as hitherto 

 assumed from Mr. Thomson's observations. Because 

 Watson's Island has so many advantages over the old 

 standardizing station, Mr. Sanderson was asked to ob- 

 tain further observations on the reef before the Carne- 

 gie's return in November. For this purpose, Mr. Park- 

 inson movmted a new pair of fibers in the observatory 

 electrometer and left two more sets, with a mounting 

 device and other equipment, the observatory having no 

 spare fibers and no means of moimting them. 



It may be mentioned that at the time of the eye ob- 

 servations on Watson's Island on April 11, the condition 

 on the Carnegie was "MDBS awning up" and the mean 

 reduction factor obtained for the Carnegie recorder for 

 the five-hour period was 3.14. The mainsail had to be 

 lowered during this time as there was a stiff breeze, 

 but it is probable that the position of the boom rather 

 than that of the sail is the controlling factor. 



Conductivity Apparatus 8A-. --Unusuallv high values 

 of Insulation-leak prevailed for a few days early in May. 

 Thorough cleaning of all the insulators did not immedi- 

 ately remedy the defect, which disappeared of its own 

 accord about May 10. 



Ionic Content Apparatus 1 .- -During the damp night 

 hours of the diurnal -variation runs of April 30 and May 

 1 and May 9 and 10, high insulation leaks developed and 

 could not be eliminated. Apart from this the apparatus 

 has worked perfectly well. 



Penetrating Radiation Apparatuses 1 and 5503. -- 

 Speclal attention has been given to comparisons between 

 these two instruments. The first attempt to obtain a 

 comparison of values between numbers 1 and 5503 

 mounted in an exposed position on the quarter-deck was 

 made on May 16. It was soon found that heating up of the 

 chaml>er by the sun gave abnormally high values. Dur- 

 ing the diurnal -variation run of May 27 and 28, no. 5503 

 was first used inside the atmospheric-electric labora- 

 tory, then at sundown it was mounted on the quarter- 

 dedc, and it was brought inside again at sunrise on the 

 twenty-eighth. It was foxind that the mean ratio of no. 

 5503 to no. 1 for the night observations was less than 

 unity, a result which was probably influenced by tem- 

 perature effects. A grouping was made of all compari- 

 son observations taken in the laboratory between May 2 

 and 30 to show how the value of this ratio is related to 

 the temperature of 5503. Of course many more obser- 

 vations will be needed before any temperature correc- 

 tion can be deduced. Here it should be mentioned that 

 the thermometer attached to no. 5503 is difficult to read 

 accurately without a reading glass and it is clear that 

 more than one reading will have to be made in the future 



